Great Northern Railway was a colorful transcontinental rail line (1857-1970) which ran from Chicago northward along the USA/Canada border, serving both nations, and to Washington, Oregon and California on our West Coast. Its famous herald was of a mountain goat within a circle. It eventually merged with NP, CB&Q, and SP&S to form the Burlington Northern Railroad until 1996 when the BN merged with ATSF to become BNSF.
When helpful and profitable uses for woodchips were realized after mid-century and they transcended being "trash," there was a scramble to figure out a way to transport them via the railroads. Old hopper cars, both ribbed and offset were pressed into service. The addition of "extended tops" made the transport of the lighter-than-coal chiploads effective and productive. All manner of tops were conceived, from wood planking and braced ply-boards to welded steel sheeting and scrap siding.